Our house is slowly sinking. We are having a company come and put in piles and raise the house. The guy that came to check our house had a level that I can’t find any literature on. It looks like a canister vacuum cleaner with a really long tube that the guy could carry around from place to place measuring the relative height at each location. He claimed the tube was filled with some gas. I suspect it would be freon or something that condenses easily, since I can’t see how a gas could be used to detect minute level changes.
I believe that he called it a comp level, but google brings up nothing.
This works by water seeking its own level even though it is contained in a U-shaped tube with an arbitrary length of tubing forming the bottom of the U. Even if you go around a corner from the other end of the level, the water level shown in the tube in your hand will match the level at the other end.
But you said the guy mentioned gas, so it might be nothing of the sort.
It didn’t look anything like that unfortunately. I still tend to think a manometer type level might make sense. If it were compressed freon, the laypersons might still think that it is a gas, because if it is punctured, a gas would escape.
OTOH, he operated it by leaving the “base” on the first floor and running the long tube down to the various points in the basement. I assume, he was checking height relative to the base, that was on a completely different floor. I’m not sure how a manometer type level would do that.
You can resolve a little under a foot with a decent absolute pressure transducer and low noise electronics, but inch level resolution is really not doable. Barometric pressure often changes quite quickly when measured at that scale as well, so you’d need to take all your measurements within a minute or so.
Certainly not doable indoors due to pressure fluctations from HVAC, wind blowing on open windows etc.
They are still claiming it has something to do with pressures of gasses. It is apparently very sensitive to temperature fluctuations along the line. That is pretty consistent with the behavior of gases.